https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96075
--- Comment #5 from rguenther at suse dot de <rguenther at suse dot de> --- On Mon, 6 Jul 2020, rsandifo at gcc dot gnu.org wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96075 > > --- Comment #4 from rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.org> > --- > (In reply to Richard Biener from comment #3) > > So we end up calling get_negative_load_store_type for this group which seems > > to only handle contiguous accesses but this one is single element > > interleaving > > aka contiguous with gap. > > > > vect_supportable_dr_alignment returns dr_aligned which is seemingly OK for > > > > #(Data Ref: > > # bb: 3 > > # stmt: _4 = y[_2]; > > # ref: y[_2]; > > # base_object: y; > > # Access function 0: {1022, +, -2}_1 > Are you sure we support this? I think… > > > /* If this is a backward running DR then first access in the larger > > vectype actually is N-1 elements before the address in the DR. > > Adjust misalign accordingly. */ > > if (tree_int_cst_sgn (step) < 0) > > { > > tree offset = ssize_int (TYPE_VECTOR_SUBPARTS (vectype) - 1); > > /* DR_STEP(dr) is the same as -TYPE_SIZE of the scalar type, > > otherwise we wouldn't be here. */ > …really was the assumption for negative steps at one time, > and I'm not sure off-hand when/if that changed. > > (Of course, it might be that one of my patches changed it.) Yeah - me too. We still don't seem to support those for interleaving [single element] groups but we let them slip through for SLP ... That said, the patch shouldn't make the situation worse at least ;)
